What is the diagnosis/impression for a patient with severe iron‑deficiency anemia (hemoglobin <7 g/dL, low ferritin, low transferrin saturation, inappropriately low reticulocyte count) likely secondary to chronic gastrointestinal blood loss, to include in a referral?

Diagnosis/Impression for Referral

The diagnosis is severe iron-deficiency anemia (IDA) secondary to chronic gastrointestinal blood loss, with inappropriately low reticulocyte response indicating inadequate bone marrow compensation.

Primary Diagnostic Formulation

For a referral to another institution, the diagnosis should be structured as follows:

• Severe iron-deficiency anemia (hemoglobin <7 g/dL) with laboratory confirmation of absolute iron deficiency (low ferritin, low transferrin saturation <16-20%) 1
• Inappropriately low reticulocyte count indicating inadequate erythropoietic response despite severe anemia, which suggests either profound iron depletion preventing effective red cell production or possible concurrent bone marrow suppression 1
• Suspected chronic gastrointestinal blood loss as the underlying etiology requiring urgent gastroenterological evaluation 1

Key Diagnostic Elements to Include in Referral

Laboratory Confirmation of Iron Deficiency

The referral should specify the iron studies that confirm absolute iron deficiency:

• Serum ferritin <30 μg/L (in absence of inflammation) or <100 μg/L (if inflammatory markers are elevated) confirms depleted iron stores 1
• Transferrin saturation <16-20% indicates inadequate iron delivery to bone marrow for erythropoiesis 1, 2
• Low mean corpuscular volume (MCV) and low mean corpuscular hemoglobin (MCH) documenting microcytic, hypochromic anemia characteristic of iron deficiency 1

Critical Reticulocyte Finding

• The inappropriately low or "normal" reticulocyte count in the setting of severe anemia (Hb <7 g/dL) indicates the bone marrow cannot mount an adequate compensatory response, which is consistent with severe iron depletion preventing effective erythropoiesis 1
• This finding excludes hemolysis (which would show elevated reticulocytes) and confirms that deficiency—not increased red cell destruction—is the primary mechanism 1

Indication for Urgent Gastroenterology Referral

The referral should emphasize the need for urgent investigation:

• Chronic GI blood loss is the presumed etiology and requires endoscopic evaluation to exclude gastrointestinal malignancy, particularly in patients over age 50 or with alarm symptoms 1, 3
• The British Society of Gastroenterology guidelines recommend that investigation should be considered at any level of anemia in the presence of iron deficiency, with stronger indication for severe anemia (Hb <110 g/L in men, <100 g/L in non-menstruating women) 1
• Colonoscopy is the preferred initial endoscopic procedure for patients over 50 years, though bidirectional endoscopy may be warranted depending on clinical context 3

Additional Diagnostic Considerations to Document

Rule Out Concurrent Conditions

The referral should note whether the following have been excluded:

• Inflammatory markers (CRP, ESR) should be documented, as ferritin is an acute-phase reactant and may be falsely elevated in inflammation, potentially masking iron deficiency 1, 2
• Vitamin B12 and folate levels should be checked to exclude combined deficiency, particularly if MCV is normal despite iron deficiency (suggesting concurrent macrocytic process) 1
• Renal function (creatinine, GFR) to exclude chronic kidney disease as a contributing factor to anemia 1, 2

Severity Indicators for Triage

Document the severity to facilitate appropriate triage:

• Hemoglobin <7 g/dL represents severe anemia with significant risk for cardiovascular complications and impaired quality of life 1
• The combination of severe anemia with inappropriately low reticulocyte response indicates profound iron depletion requiring urgent investigation and likely parenteral iron replacement 1, 2

Common Pitfalls to Avoid in Referral Documentation

• Do not assume normal ferritin excludes iron deficiency if inflammatory markers are elevated, as ferritin rises with inflammation and may mask depleted stores; in inflammatory states, ferritin <100 μg/L suggests iron deficiency 1, 2
• Do not delay investigation waiting for response to oral iron therapy in severe anemia with suspected GI blood loss, as this may delay diagnosis of malignancy 1, 3
• Do not attribute anemia solely to "anemia of chronic disease" without documenting transferrin saturation; if TSAT <20% with ferritin 30-100 μg/L, this indicates mixed iron deficiency and anemia of chronic disease requiring both treatment of underlying condition and iron supplementation 1, 2

Suggested Referral Language

"Severe iron-deficiency anemia (Hb <7 g/dL) with laboratory confirmation of absolute iron deficiency (ferritin <30 μg/L, transferrin saturation <16%) and inappropriately low reticulocyte count, indicating inadequate bone marrow compensation. Suspected chronic gastrointestinal blood loss as underlying etiology. Urgent gastroenterological evaluation requested to exclude GI malignancy and identify source of blood loss." 1, 2